High voltage discharge tube with a reentrant type anode terminal



y 1969 J. F. STEPHENS ETAL 3,456,147

HIGH VOLTAGE DISCHARGE TUBE WITH A REENTRANT TYPE ANODE TERMINAL FiledFeb. 1. 1967 FIG.

E: ull; um.

INVENTORS: JOE F. STEPHENS,

DAN M.WILSON,

IR ATTORNEY.

United States Patent 3,456,147 HIGH VOLTAGE DISCHARGE TUBE WITH AREENTRANT TYPE AN ODE TERMINAL Joe Stephens and Dan M. Wilson,Owensboro, Ky., assignors to General Electric Company, a corporation ofNew York Filed Feb. 1, 1967, Ser. No. 613,338 Int. Cl. H01j 1/88, 19/42US. Cl. 313-247 Claims ABSTRACT OF THE DISCLOSURE This invention relatesto electric discharge devices, and more particularly to high voltagedischarge devices, such as high voltage rectifiers.

In high voltage discharge devices it is necessary that the externalleads which connect to the electrodes within the device be spacedsufficiently far apart so that corona or arcing is prevented. Thus, inthe usual high voltage rectifier the cathode is connected to theexternal circuit through lead pins sealed through the base of theenvelope while the anode lead, or top cap, is sealed through the dome ofthe envelope. The height of the envelope from base to dome was usuallygreat enough to provide suflicient distance between the cathode andanode leads to avoid corona.

With the need to miniaturize such discharge devices, the height of theenvelope has been attempted to be reduced by providing more insulationaround the external connections. Such attempts have been relativelyuneconomic solutions.

With the need for high voltages to be handled by such devices,particularly for color television receivers, an even greater demand onprevention of corona has been made. To merely make the height of thedevices great obviates against the need for small devices. An object ofthe invention is to provide a high voltage discharge device whichsatisfies the above needs.

Another object of this invention is to provide a high voltage dischargedevice which reduces the overall height of the device. A further objectof the invention is to provide an electric discharge device for handlinghigh voltages which substantially eliminates the need for heavilyinsulated connectors thereto. A still further object of the invention isto provide a high voltage discharge device which may be more easily andeconomically connected to its external circuit.

In accordance with the aforementioned objects, there is provided a highvoltage discharge device comprising an anode and a cathode mounted inspaced relationship within a sealed insulative envelope, a conductivelead for each of said electrodes sealed in said envelope at oppositeends thereof, one of said leads being a hollow tubular member, having anopen end and a closed end, said closed end being within said envelopeand the edge of said open end being sealed to the envelope.

Further objects and advantages of the invention will be understood fromthe following complete description of the preferred embodiment thereofand from the drawing wherein:

3,456,147 Patented July 15, 1969 FIG. 1 is a perspective view of anelectron discharge device constructed in accordance with the preferredembodiment of the invention;

FIG. 2 is an enlarged section view of a portion of said device; and

FIG. 3 is an enlarged section view of the seal.

As shown in FIG. 1, a high voltage rectifier incorporating the inventionincludes a sealed glass envelope 3 of lead or borosilicate glass. Saidenvelope may have on its interior surface a coating of semiconductivematerial such as lead or chrome oxide to protect the envelope from ionbombardment. The high voltage discharge device further includes a deepdrawn inverted cup-like anode 4 mounted within the envelope and acathode 5 mounted within the confines of the anode 4. The cathode 5 ismechanically supported, and electrical connection may be made thereto,by a pair of conductive leads 6 and 7. The conductive leads 6 and 7 aresealed in the base portion 8 of the envelope 3 with pins 9 and 10extending outwardly therefrom for external electrical connection of thecathode 5. While, as shown, the leads 6 and 7 are individually integralconductive members they may be constructed as a plurality of piecessecured together as by welding. The cathode 5 is illustrated as afilamentary directly heated cathode but may be an indirectly heatedcathode as well.

The inverted cup-like anode 4 is supported, and electrical connectionthereto may be made, by an anode lead 11 sealed in the opposite end, ordome, 12 of the envelope 3 so that a maximum distance is affordedbetween the anode lead 11 and the cathode pins 9 and 10 to preventcorona therebetween. The anode lead 11 includes a solid rod, or wire, 13and a thin-walled tubular cup-like leadshell 14 having an end wall 15and an open end 16. The rod 13 is secured at its ends to the anode 4 andthe anode lead-shell 14, respectively, by percussive welds 17 and servesas a low thermal conductivity path therebetween while mechanically andelectrically connecting them. The open end 16 of the anode lead-shell 14is secured in the dome 12 of the envelope by a seal 18.

The seal 18 (FIG. 3) is formed around the end edge 16a of open end 16 ofthe anode lead-shell so that it is a multiple surface seal. Thus, asillustrated, the glass of the seal 18 coats, and is fixed to, the outersurface 16b, the inner surface 16c, and the end edge 16a, of the openend 16 of the anode lead-shell 14. The multiple surface seal 18 has, inaddition to the greater seal area afforded, the distinctive advantagethat no conductive material edge or point is exposed from which a coronadischarge could initiate.

The anode lead-shell 14 is preferably provided intermediate its endswith a circumferential constriction or rib 19 to constrain movement ofthe external connector 20 of the type to be used in connecting the anodeto the external circuit. The connector 20 as illustrated, can with thehigh voltage discharge device of the present invention be simply aconductor 21 coated with insulation 22 upon which a conductive end piece23 has been crimped. The external connector 20 may be pushed into theanode lead-shell 14 so that the rib 19 exerts a radial force thereon andprevents its inadvertent withdrawal. The cup-like shape of anodelead-shell 14 by extending into the interior of the envelope andsurrounding the only exposed conductive part of the connector 20 (theend piece 23) obviates the need for any insulative structure on theconnector as was heretofore required. Thus, in effect, the envelope 3 ofthe discharge device acts as the insulative cover for the externalconnector as well as the electrodes of the device itself.

As more completely described in copending application S.-N. 613,266filed herewith, the anode 4 and anode lead 11 can be easily manufacturedand sealed into the dome 12 of an envelope 3 by first percussivelywelding the rod 13 to the anode 14 and the anode lead-shell 14 aspreviously indicated. The welds 17 may be made separately orsimultaneously. A bulb with the dome intact is then placed over theassembly with the open end 16 of the lead-shell 14 in contact with thedome 12 of the bulb. A centered overhead flame is directed at thatportion of the dome which is contacted by the lead assembly. The flamedepresses the softened bulb into the interior of the anode lead-shell 14and then pierces it, and the open end 16, being in contact with theinterior surface of the dome, confines the piercing to that smallportion of the dome. Continued application of the flame heats the anodeleadshell to the proper temperature, approximately 850 C., at whichbonding of the glass to the metal will occur. At this temperature asmall amount of molten glass flows over the inner and outer surface ofthe anode lead-shell forming the multiple surface seal 18. As the partsare cooled and annealed the anode assembly is pulled inwardly so as todepress the seal 18 approximately 0.1 below the uppermost surface of thedome. The base 8 with the cathode pins 9 and 10 sealed therein andcathode 5 mounted upon leads 6 and 7 is sealed to the bottom end of thebulb. The assembly is completed by heating the electrodes, particularlythe anode 4 so as to cause outgassing of the parts. During thisextensive heating of the anode the rod 13 prevents sufiicient heat frombeing conducted to the area of seal 18 to cause rupture thereof. Theenvelope is exhausted and the tip-off 8a formed to complete the device.

From the above, it will be seen that there is provided a high voltagedischarge device which has a reduced height since the anode connectionis within the confines of the envelope and does not extend externallytherefrom 'while still maintaining the anode connection at a properdistance from the cathode leads. The anode connection further provides asmooth, unipotential surface which prevents corona initiation. Also, theanode-lead permits the use of a simple economic external connector to beused therewith since the insulative envelope of the device serves as theinsulator for the connector.

While the invention has been disclosed as useful for rectifiers, it willbe understood that similar caps could be used for other high-voltagedischarge devices, including multi-element devices, such as televisionhorizontal deflection amplifier pentodes.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A high voltage discharge device comprising an anode and a cathodemounted in spaced relationship within a sealed insulative envelope, aconductive lead for each of said electrodes sealed in said envelope atopposite ends thereof, one of said leads being a hollow tubular memberhaving an open end and a closed end and a constricted portionintermediate said ends, said closed end being within said envelope andthe edge of said open end being sealed to the envelope.

2. A high voltage discharge device as recited in claim 1 wherein saidhollow tubular member has a constricted portion intermediate its ends.

3. A high voltage discharge device comprising an anode and a cathodemounted in spaced relationship within a sealed insulative envelope, aconductive lead for each of said electrodes sealed in said envelope atopposite ends thereof, one of said leads comprising a hollow tubularmember having an open end and a closed end, said closed end having asmall diameter rod member secured thereto at a first end of said rodmember, the other end of said rod member being secured to one of saidelectrodes, said closed end of said tubular member being within saidenvelope and the edge of said open end being sealed to the envelope.

4. A high voltage discharge device as recited in claim 3 wherein saidone electrode is an anode and said rod provides a thermal barrier meansbetween said anode and said hollow tubular member.

5. A high voltage device as recited in claim 4 wherein said hollowtubular member has a constricted portion intermediate its ends.

References Cited UNITED STATES PATENTS 2,613,336 10/1952 Doolittle313-247 X 2,797,348 6/1957 Watrous 313--247 X JAMES W. LAWRENCE, Primaryexaminer C. R. CAMPBELL, Assistant Examiner

